Centrifugal pump



March 23,1926. 1,578236 H. E. LA BOUR CENTRIFUGAL PUMP Filed March 4,1922 2 Sheets-Sheet 1 March 23 1926. 2 1,578,236

' H. E. LA "BOUR CENTRIFUGAL PUMP Filed March 4, 1922 2 Sheets-Sheet 2Java/2601 arm/ 5 Patented Mar. 23, 1926:

UNITED- STATES PATENT omen.

Application filed March 4, 1922. Serial 110. 541,030.

To all whom. it may concern. Be it known that I, HARRY LJLE Bonn,

' citizen of'the United States, residin at -Chicago, in the county ofCook and tate of Illinois, have invented a certain new and usefulImprovement in Centrifugal Pumps, of which the. following is a full,clear, concise, and exact description, reference be ng had to theaccompanymg drawings, formlng a part of this specification.

My invention relates to centr fugal pumps. The pump which I- shalldescribe 1n connection with the following specification as being thepreferred embodiment of my invention has a novel characteristic in thatit operates both by injection and momentum to discharge a greaterquantity of liqu1d than would appear to be possible when consideringmerely the capacity of the pocket and the speed of rotation of theimpeller.

My explanation of this feature is, that the v pump operates not only onthe principle of the well known centrifugal pump by throwing fluidoutwardly by centrifugal; action, but also that it operates on theinjection principle. It is well known that while a column of liquid ismoving, it has a very considerable inertia and sudden stoppage or changeof direction often causes a liquid to evidence the inertia that it hasto avery considerable degree. In the present case I provide an open pumprunner having an open spider with a ring upon its outer periphery, thisring having transverse blades or impellers which project radially andlat orally from the sides of the ring to form U- shaped pockts, bothlegs of the U being open and the bottom of the U being closed by thenormal inner'periphery of the pump casing. The casing provides a channelor race-way fitting quite closely about these pins or blades. At thepoint where the discharge is to occur, the bottom of the channel is re?moved to provide a discharge or outlet opening which may be andpreferably is substantially tangential. At this point the bottom of eachU-shaped slug of water is permitted to move radially and the arms of theU follow it. Since the inner ends of the arms of 0 the U open into theliquid upon the interior of the ring the movement of the Utends to drawliquid in andelongate the arms of the U so that more actual liquid thanthat which fills the U-shaped pocket actually does pass out thedischarge giving the pump a greater displacement than would emptying ofthe pocket.

Another feature of my invention relates to the means for making thispump selfpriming so that it may operate as a suction pump to liftliquids a very considerable distance within suction limits. I provide aseparating chamber upon the discharge side of the pump for separatingliquid from as and near the lower part of this separating be caused bymere chamber I provide a connection which delivers liquid to the pumpthrough an auxiliary inlet, this inlet entering the pump nearthe-outerportion of the impeller, and preferably substantially radially of theimpeller at a point adjacent the outlet, but posterior thereto withregard to the direc- Upon the intake side of the pump I provide a -trapfor trapping a certain amount of liquid sufiicient to start theoperation of the pump as a suction pump, this amount of liquid beingonly great enough to fill the pump chamber, the bottom of the separatorand the auxiliary intake, to maintain the runner substantially full ofliquid. A further feature of novelty comprises the provision [of aremovable and self-cleaning strainer of relatively large size in thesuction pipe.

The impeller is of a self-balancing type, that is, having no thrust sothat no additional bearing is required for this purpose.

'In order toacquaint those skilled in the art with the manner ofconstructing and using a pump according to my invention, I shallnowdescribe in connection with the accompanying drawings one embodiment ofthe invention;

Figure 1 is a vertical cross-sectional view of a pump of theself-priming type embodying my invention;

Fig. 2 is a vertical cross-sectional view taken at right angles to thesection of Fig. 1 of the same;

Fig. 3 is a front elevation;

Fig. 4 isa side elevation of a pump embodying my invention omitting theselfpriming feature; and

Fig. 5 is a fragmentary view of a modified form of impeller.

As shown in Fig. 2 the pump casing comor substantially no endtion ofrotation of the runner or impeller.

prises the front half 1 and the rear half 2, these parts being boltedtogether by suitable flanges thru which bolts are passed for clampingthe halves of the casing together. The rear half 2 has a foot plate 3for supporting the pump. This foot plate isjolned to the rest of itscasing portion by the integral webs'5 and 6,.as shown in Fig. 1, and ,I

atth1s point. In

the stiffening web 7 on the back, this stiffening web merging into thestuifing box 8 thru which passes the shaft 9 for the impeller 10. Thefront half 1 comprises a flaring inlet portion 11which has a flangedinlet opening 12, the flanges 13 of which are adapted to be joined tothe cooperating flanges 14. of the trap member 15. This trap member 15extends upwardly and has an inlet opening at 16 sufliciently above itsoutlet opening 17 as to trap a body of liquid suitable for priming thepump. The flanges 18 at the inlet opening of the trap member 15 areadapted to be connected by suitable flanges19 to the suction or inletpipe 20.

It is to be noted that the inlet opening through the flange 18 is madeslightly larger than the outlet from pipe 20. This is done to provideroom for the screen 47 which comprises a suitable short length of pipeprovided with perforations to form a screen. The inner end of. thescreen rests upon a ledge 48. The inner end of the screen is closed offby the wall 49 of the trap 15. The

outer end of the screen is held in the opening through the flange 18 bythe pipe 20 and cooperating flange 19. As will be pointed out later,when the pump is stopped, the liquid in the discharge pipe tends toforce its Way back through the pump and through the suction pipe untilair passes over. This back flow tends to clean the screen 47. Thisscreen is accessible by releasing the flange 19. Thus the screen may becleaned without disturbing the trap or losing the priming charge ofliquid. The total area of the holes'through the side walls of the screenis considerably in excess of the cross sectional area of the pipe out ofwhich it is formed, so that little or no restriction is formed by saidscreen. Any foreign substance large enough to damage the impeller 10will be stopped by' the screen 47.

The trap 15 is bolted to the flange 13 by suitable bolts, the upper onesof which pass thru bosses 51, extending thru the trap 15. If desired aseparate support may be provided for the trap 15 since it is quiteheavy. The two halves of the casing are generally circular, the upperpart being provided with two bosses 21 for forming the discharge, and 22for forming the auxiliary inlet nozzle. The discharge has flanges 23'and 24 formed on the corresponding halves of the casing so as to form acomplete circular flange about the discharge port 25 of the pump.- Thedischarge port is flared" upwardly as is apparentt from Fig. 2, and itis flared out peripherally of the impeller 10 to form a fairly widedlscharge opening 26, as is shown in Fig. 1. This discharge port- 26 iswidened immediately beyond the ends of the impeller blades to permit thefluid to expand laterally impeller. This reduces the friction of flow asimilar manner the boss 22 provides the auxiliar leads in substantiallyra ially towards the impeller 10. This port is also flared to formpockets in the sides of the casing, which extend downto a point belowthe ends of the impeller blades, maintaining, however, a seal along thesides of the impeller as indicated at 50. The boss 22 is similarlyprovided with bolting flanges formed on the corresponding halves of thecasing. A fitting 28 which I term the gas separating chamber, isconnected by means of a suitable bolting flange 29 to, the flanges23-24, surrounding the discharge port 25. This fitting constitutes anenlargement in the discharge pi e 30 of which it forms a part. Anopening or port 31 is formed in the wall of the fitting 28 and this isconnected by a suitable flanged pipe 32 to the auxiliary inlet 27.

Where the pump is to be employed without the self-priming feature, theseparating chamber 28, the connection 32 and the inlet trap fixture 15are omitted, as is shown in Figures 3 and 4. In that event, theauxiliary inlet passageway 27 is closed by a plate 33 which is'bolted tothe flanges on the boss 22. The discharge pipe 30 without anyenlargement is then clamped directly to the flanges 23.24 on thedischarge nozzle 25, and the intake pipe 20 with its flange'19 isconnected directly to the intake opening 12 of the front half of thepump casing. The impeller or runner 10 forms, 1n connectionwith thecooperating casing, a novel structure having a very highly advantageousoperating characteristic. The runner 10 comprises a centralhubmenr ber35 from which radiates a plurality of arms 36, in the present instance 8in number. Integral with the ends of the arms 36 I. have formed a flatring 37 which appears in side elevation in Fig. 1 and in sec tion inFig. 2. A series of vanes or impellers 38 are formed on the ring 37preferably cast integral therewith, these blades or vanes extending outlaterally from both sides of the ring 37 and extending outradially inasimilar manner to form pockets which are U"-shaped with the legs of theU communicatingfreely with the liquid in the central part of the casing.To permit this, the

port 27 which flared inlet connection 11 communicates free-- lv with.the adjacent open ends of the U- shaped pockets and the casing is soformed that the rear wall 39 of the back half of the i ployed. I findtheone illustrated casing provides a free space which communicates withthe other leg of the U-shaped pocket. The space 40 communicates with thespace 41 in the flared portion 11 throu h the 0*en spider of theimpeller 10. ll lie impel or may be constructed in any'other mannerwhich will secure the same result. A closed runner or impeller may beempreferable but do not intend to limit the invention thereto. M i

The two halves of the casing provide an interior peripheral channel 42which fits closely about the blades or \HIILS 38 with only the necessaryoperating clearance between the casing and the blades of the impeller.The peripheral channel 42 is unbroken except at the discharge port 26and the auxiliary inlet port 27. It will be noted from Fig. 1 that theadvance or anterior edge of the discharge port 26 is substantial- 1ytangent to the channel 42 across the full width thereof. This openingextends preferably across the full width of the channel 42. Theposterior or trailing edge has less inclination and it has a wall curvedgently at 43 for merging into the vertical discharge nozzle 25. Thechange of direction of the fluid is thereby effected with a minimum lossof head. There is also a clearance 52 at the trailing corner of thedischarge port 26 to prevent eddy currents at this point.

The leading or anterior edge of the port 27 is substantially radial tothe impeller 10 while the trailing or posterior edge is rounded oif asshown at 53 to diminish the friction to the flow of liquid at thispoint. The port. 27 opens into said channel 42 preferably across thefull width of the same and has in addition thelateralpockets adjacent50. The rear half 2 of the casin has a forming flange 53 which extendsparallel to the axis of shaft .9 to bring thejoint between halves overto one side of the channel 42. This flange assists in centering the,

halves 1 and 2.

The operation of the device shown in Figs. 1 and 2 is as follows:

Assuming that the inlet trap 15 is filled .with liquid to the level ofthe bottom of the intake port 16 and that the liquid stands 'at an equalheight in the pump and the discharge connections, the pump may be causedto evacuate the gas such as air or the like in the suction pipe, 20 byrotation of the impeller 10, counter-clockwise in Fig. 1, as in dicatedby the arrow. Rotary movement of the impeller 10 tends to throw thewater in each of the pockets formed between the vanes or impeller bladesto the bottom of the channel 42. The slug of water contained in each ofthese pockets is substantially U-shaped, the bottom of the U re:tingagainst the bottom of the channel 42 and the sides of the U beingrestrained between the sides the result that a continued refilling ofthe legs of the U results until the pocket passes under the trailingedge of the port 26. If insufiicient liquid is present in the body ofthe'pump, the gas itself will tend to follow each slug with the resultthatbetween the slugs of water discharged through the dis charge port 26there are expelled small bodies of gas,-which together with the waterare expelled through the nozzle 25 into the gas separating chamber 28,the gas rising above the water and the water tending to drop down andpass through the port 31,

fitting 32, into the auxiliary admission port at .27 where unmixedliquid is fed back into the channel to fill the pockets of the impelleras they pass. It is to be'noted that if the upper part of the pumpcontains air, then r the pockets as they pass the discharge port 26 arecompletely emptied and they cannot, therefore, create any materialpressure against the incoming of liquid at the auxil; iary inlet port orpassageway 27. The result is that the liquid freely reenters through thepassageway to keepthe pockets primed between the auxiliary inlet port 27and the discharge port 26 in the direction of rotation. If, however, thegas has been exhausted from the suction pipe 20 and-from the casing ofthe pump so that liquid fills the casing of the pump, the pressuredeveloped by the liquid in the pockets after they pass the trailing edgeof the discharge port 26 rises to a pressure substantially equal to thepressure prevailing in the inlet 27 whereby thereis substantially nointerchange of liquid between them. In fact, by suitable proportioning,the pressure developed by the impeller may rise to a value high enoughto cause adischarge of liquid from the pockets into the auxiliary inlet27 during normal operation.

This is a novel feature and new mode of operationnot attained in anypump with which I am familiar, namely, that I have an auxiliary inletport which operates during the priming period as a means for per- I thedischarge opening.

' that it is highly desirable that the discharge pocket The injectoraction which this pu secures is not limited to the particu ar s ape ofimpeller, although I have found that the particular impeller which Ihave illustrated is preferable. It is not necessary that the form aU-shaped slug, since the ring 37 may be extended out to the bottom ofthe channel 42 and be given a zig-zag form, as I have shown at 37 f inFi 5. Here pockets 5,45 are formed alternately upon opposite sides ofthe ring 37, this ring being mounted directly upon the ends of theSpider arms 36. 'It is necessary that the pockets be open at towards thecenter when the outer end of the pockets register with the dischargeport 26, so that the outward throw of the slug of Y water contained inthe pocket may induce;

a flow through the pocket while the same is in register with said port26. The impeller which I have shown gives a balanced effect since liquidis drawn equally from each side of the ring so that no end thrust in theimpeller is developed. It is desirable that. the blades or vanes extendclosely adjacent to the bottom of the channel 42 in order to securemaximum effect. It is not desirable so far as I have found to have aradial flow of liquid through the pockets as is customary in theordinary volute pump, except during that period when the pocketsregister with The pump is highly effective whether used with heself-priming feature or not. Where the self-(priming feature is notrequired, the auxiliary inlet may be closed by a plate as indicated inFigures 3 and 4,. and the inlet and discharge are then directlyconnected to the pump casing without the inlet trap and the gasseparator. That the injector action does occur as stated is evidenced bythe fact that the discharge of a pump of this char- 1 acter is verygreatly in excess of the'quan-- tity which would be discharged by mereemptying of the pockets at a given speed. Thus, for instance, I findthat for a .oneinch size pump operating at 1800 R. I. M. thedisplacement capacity of the pockets alone would be approximately 15gallons per minute. I have found that it is possible to discharge liquidgreatly in excess of 15 gallons per minute. For instance, I find that itis possible to deliver gallons per minute with this pump against apressure of 14 unds head.

' 1 do not intend to be limited to the precise construction shown anddescribed, since considerable modification is possible without departingfrom my invention.

. There are several features to which I wishto call attention in thisconnection. First,

port 26 be at substantially the highest point in the pump casing so thatthe air which the rear or at the'end which faces separates from theliquid by gravity will be readily and completely withdrawn.

Another feature to which I wish to call attention is the auxiliary inletport 27. The advanced edge of the auxiliary inlet port 27 issubstantially radial, while the trailing edge is rounded. The result isthat a slug of liquid finds difliculty in moving out of the pocketinto=this auxilia inletport when the pump isf'ull of liquid. Theauxiliary inlet passageway isshaped however, to promote the introductionofliquid into the impeller when the top'of the impeller is otherwiseoccupied by air or gas. 7

It is not essential that the liquid for the auxiliary inlet 27 beintroduced from the discharge pipe, it may be introduced from anyconvenient source. 'not essential that the auxiliary inlet port It is,furthermore,

open at the'top of the pump although this is more desirable to securegreater eflic-iency and better balance.

'I claim:

1. The method of operating a centrifugal pump which comprises rotatingthe impeller and simultaneously introducing liquid peripherally intotherunner independently of the main source of liquid.

I 2. The method of'exhausting gas from a centrifugal pump whichcomprises rotating the impeller and simultaneously introducing liquidinto the impeller at apoint remote from the normal inlet of the pump.

3. The method of priming a centrifugal pump containing gas, whichcomprises ro-' tating the impeller and simultaneously introducmg liquidperlpherally into the impeller at a point posterior to the normaldischarge opemng.

4. A pump comprising a casinghaving an internal peripheral channel, adischarge port openmg from said channel at substantially the highestpoint thereof, an inlet opening laterally into the casing, a peripheralinlet port opening into said channel at a point adjacent but posteriorto the discharge port, and a pump runner for throwing successive slugsout of the discharge port, said pump runner having pockets communicatingat their interior with the contents of the casing. 4 I

5. A pump comprising a casing having a central inlet, a peripheraloutlet and a constantly opened auxiliary inlet connected to said outlet,an impeller having blades in said casing, said inlet being subject tothe centrifugal force of the liquid inthe pump to render it lesseffective when the pump is filled with liquid than when it is onlypartly filled with liquid, most of the area inside said blades beingaxially open.

6. A pump'comprising a casing having a central suction inlet for liquid,a runner lying in a vertical plane, a peripheral outlet at substantiallythe highest :oint in the easing, and means for introducing liquidperipherally into the casing when the pump is only' tartly filled withliquid.

7. A pump comprising a casing having an interior peripheral circularchannel and having a tangential outlet opening into said channel, animpeller having a peripheral member closely fitting within said channel,said' peripheral Imember defining pockets opened at both ends radiallywith respect to the axispf the impeller.

-8. A pump comprising a circular interior channel having a tangentialdischarge port, an impeller having a peripheral member closelyv fittingwithin said channel, said peripheral member comprising a ring havingpockets at each side thereof, defined, in part, by the side of thechannel, said pockets being open radially at both ends. v v

9. In a centrifugal pump, a closed casing having an inlet, a peripheraloutlet and an auxiliary inlet opening peripherally into the casing, saidauxiliary inlet being constantly open and subjected to the internal"pressure of the casing.

10. In a centrifugal pump, a closed casin'g having an inlet, aperipheral outlet and an auxiliary inlet opening peripherally into thecasing, said auxiliary inlet being connected with the outlet.

11. In a centrifugal pump, havin a closed casing, a horizontal impellersha t in the casing, an intake, a peripheral discharge opening arrangednear the top of the casing and a constantly open auxiliary connectionentering the casing near the discharge opening and on the posterior sideof the same with relation to the direction of rotation of the impellershaft.

12. Ina centrifugal pump, having a casing, an impeller lying in avertical plane in the casing, an intake, a tangential discharge openingand an auxiliary inlet connection opening substantially radially intosaid casing.

13. As an article of manufacture, a pump runner including a centrallydisposed spider, said spider having a plurality of radial arms, acircular element mounted on the arms of the spider, and a plurality ofblades formed on said element and projecting radially beyond theelement, most ofthe area inside said element being axially open.

14. As an article of manufacture, a pump runner including an open andcentrally disposed spider, said spider comprising a central hub and aplurality of arms projecting radially therefrom, a shaft adapted to beassociated yvith one side of the said hub, a ring mounted on the ends ofthe arms of the spider, and transversely disposed blades formed on thesaid ring, said blades projecting from a side of the ring and projectingradially bcyond the ring, most of the area inside of the said ring beingaxially opened.

.15. In 'combinatioma ump runner including a spider, said spi er havinga plu-- rality of radial arms, a ring mounted on the arms of the saidspider, transversely disposed blades on the said ring projectinglaterally on both sides and radially from the ring, and a casing closelyfitting said blades, J

said casing having a generally central "inlet and aperipheral outlet,most of the are'ainspider arms supporting said b ades and leavinganaxially continuous open central space, a casing closely fitting saidblades or vanes, and having a. flared central inlet communicating freelywith the pockets formed by the blades or vanes.

17 A pump casing, comprising tivo halves divided along a vertical plane,one half having an opening for permitting the entry of an impellershaft,the other half having an opening in the central portion thereof servingas an inlet for-liquid, a cylindrical channel or race-way within thecasing, a runner or impeller mounted in said race-way or channel, adischarge'connection at the top of the casing, said casing having asubstan- I tially tangential outlet connection formed partly in eachhalf, an auxiliary inlet connection formed part1 in each half of thepump casing, said in ct connection opening substantially radially intosaid channel, at a point adjacent the dischargeor outlet connection,posterior to said discharge or outlet connection. t

18. A pump casing, comprising two halves divided along a vertical plane,one half'hav- 9 ing an opening for permitting the entry of an impellershaft, the other half having an opening in the central portion thereof,serving as an inlet for liquid, a cylindrical channel or race-way withinthe casing, a

runner or impeller mounted in said race:way or channel, a dischargeconnection at the top of the casing, said casing having a substantiallytangential outlet connection formed partly in each half, an auxiliaryinlet connection formed partly in each half of the pumpcasing, saidinlet connection formed partly in each half of the pump casing, saidinlet connection opening substantially radially into said channel, at apoint adjacent the discharge or outlet connection,

posterior to said discharge or outlet co-nnection and a dischargeconnection having an enlargement extending upwardly above the the pump,said outlet connection having communication with the auxiliary inletconnection.

19. A pump casing, comprising two halves divided along a vertical plane,one half having an opening for permitting the entry of an impellershaft, the other half having a central opening, serving as an inlet forliquid, a cylindrical channel or race-way within the casing, a runner orlmpeller mounted in said race-Way or channel, a discharge connection atthe top of the casing, said casing having a substantially tangentialoutlet connection formed partly in each half, an auxiliary inletconnection formed [partly in each half of the pump casing, sai inletconnection opening substantiall radially into said channel, at a point ajacent the discharge or outlet connection, posterior to said dischargeor outlet connection, anda trap" in the main inlet connection for thepump,

said trap having a portion extending above the said main inletconnection.

20. In a pump of the class described, a-

- U-shaped pockets, and an inlet connection at,

its central portion communicating freely with both legs of the U of.each U-shaped pocket.

21. The method of pumpinga compressible fluid which consists in mixingit with a liquid in an impeller chamber, throwing the mixture forciblyoutward, permitting the fluid and liquid to separate from each other,and guiding the liquid back peripherally into the impeller chamber.

22. The method of pumping a compressible fluid which consists in mixingit with a liquid in an impeller chamber, throwing-it with a velocityinto a separating chamber, generating pressure in said chamber by thearrest of the velocity of injection, and utilizing both the force ofgravity and the excess of the separating chamber pressure over intakepressure to return'the separated liquid peripherally into the impellerchamber.

23. In combination, an impeller and housing therefor shaped to agitateand mix liquid and gas, a separating chamber above said housing, adelivery conduit to deliver mixed liquid and gas at high velocity intosaid chamber, and a return conduit connected to the periphery of thehousing to return liquid separated in said chamber directly to thehousmg under the combined forces ofgravity and the pressure developed insaid chamber.

24. The method of pumping a co-mpressi ble fluid which consists inmixing it with the liquid in an impeller chamber throwing the mixturewith.velocity into a separating chamber, separating the compressiblefluid by change in direction of the flow of the mixture, and returningthe separated liquid -impeller chamber.

a 26. In a centrifugal pump, a closed pump peripherally into theimpeller chamber by the difference in pressure between said separatingchamber and the impeller chamber.

25. The method of compressing a gas which consists in mixing it with aliquid in an impeller chamber and simultaneously throwing the mixtureinto a separating chamber, permitting the gas and liquid to separate,and returning the liquid from the separating chamber peripherally intothe casing having a suction inlet, a peripheral outlet, and a constantlyopen auxiliary inlet leadin peripherally into said casing, said inletbelng externally connected to the discharge outlet.

2?. In a centrifugal pump, a closed casing having a suction inlet, aperipheral dis charge passageway, an axial inlet passageway, and anauxiliary passagewayopening peripherally into the casing, said auxiliarypassageway being supplied with liquid externall of the pump casing,-andsubjected at its inner end to the pressure prevailing in the peripheralpart of the pump casing posterior to the aforesaid discharge passageway.

28. In a' centrifugal pump, an impeller, a closed caslng having asuction inlet, a pair of peripheral outlet passageways through whichliquid is discharged in normal operation, one posterior to the otherwith respect to the rotation of the impeller, a separator, said outletsbeing connected to said separator externally of the casing, the

posterior outlet serving as an auxiliary inlet when the l1qu1d driven bythe impeller is insufficient to fill both outlets.

29. As an article of manufacture, a prime beer as to permit gases toseparate out of the liquid entering the chamberand liquid to dischargefrom said auxiliary outlet.

30. As an article of manufacture, a separating chamber for a selfpriming pump comprising a flanged inlet in the, lower part of thechamber, a flanged outlet in the to of the chamber adapted to dischargegas and liquid, an auxiliary outlet in the lower part of the chamberfordischarging liquid only, the inlet and auxiliary outlet being spacedfrom each other.

31. The method of operating a centrifbeing restricted in size to besubstantially ugal pump having a' casing and an impeller to cause it toevacuate its .suction' pipe, which comprises trapping a body of water inthe easing'in contact with the impeller, whirling the impeller to mixthe liquid with the air in the casing, drawing the mixture out of thecasing of the pump into a closed separating chamber, developing pressurein said chamber, separating the jhquid -from the air in said chamber,returning the liquid peripherally into the casing, and stopping the flowof liquid from the separating chamber when the air issubstantiallyexhausted, by the increasing peripheral pressure of thesolid liquid.

The method of operating a pump of the class described having a casingand an impeller to cause it to pickup its own liquid load, whichcomprises rotating the impeller, mixing liquid with the air in thecasing of the pump by rotation of the impeller, moving the mixture alongthe periphery of the casing, throwing out a stream of the mixture bycentrifugal force at a suitable discharge point, separating the liquidand gas under discharge pressure, returning a part of the liquid intothe periphery of the easing posterior to the point of discharge andstopping the re-entry' of said liquid into the casing by the increasedcentrifugal force developed by liquid free of gas.

33. In a pump of the class described, the combination of a casingcomprising a pcripheral channel, an impeller having ockets,

for air and water running in said 0 annel, said casing being'adapted toretain a priming charge of liquid, a peripheral port for liquid and airhaving a throat adapted to be substantially filled by the discharge fromthe impeller while the pump is operating to draw air, and an additionalperipheral port adapted to conduct liquid from the separator back intothe channel during the pumping of air, and to serve as a discharge portfor liquid when the pump is pumping liquid.

34. In combination, in a pump, a casing having a lateralinlet and aperipheral discharge outlet, a channel in said casing, an impellerhaving buckets running in said channel, said buckets opening radially atboth ends, said peripheral discharge outlet filled with the discharge ofair and liquid from the buckets when the pump is pumping air only, and aperipheral passageway forming a secondary discharge outlet for liquidwhen the pump is pumping liquid.

A pump comprising in combination, a casing adapted to contain liquid,said casing having a lateral inlet and a'peripheral discharge outlet, anannular channel in said casing. an impeller having buckets running insaid channel, said buckets opening radially at both' ends, saidperipheral discharge outlet being restricted in size to be in saidchannel, said casing having two passageways communicating. with thechannel, one of said passageways being restricted to= -a size to besubstantially filled with the discharge of air and'liquid when thepumpis drawing air, and a separating chamber joining the outer ends of bothpassageways. '37. In combination, a pump casing having a channel, asuction inlet for liquid, a pump impeller having vanes running in saidchannel, aplurality of passageways leading pe-' ripherally out from saidchannel and impeller, and a separator having means for causing theliquid to pass outfrom the one x passageway and describe a returncircuit and pass into the channel throu h-the other passageway when thepump is rawing air. 38. In combination, a pump comprising a casinghavingan annular channel, a suction inlet for liquid, an impeller having vanesrunning in said channel, a pair of passageways extending from thechannel, one of said passageways comprising a discharge pas sageway andthe other comprising a return passageway, a separator extending abovethe impeller, said. separator having means for directing the liquid andair discharged out of the discharge passageway to describe a loop withinthe separator for freeing air therein, the return passageway being of across section smaller than the discharge passageway to insure the returnof solid liquid to the impeller.

39. The method of priming a centrifugal no pump which comprises takingout through a discharge orifice amixture of gas and liquid substantiallyfilling saidorifice, checking the velocity of the mixture so dischargedand separating the gas from the liquid, returning the liquid to saidimpeller substantially free of the gas, to be again entrained with gaswithin the pump for dis charge out of said'discharge'orifice.

40. The method oi operating acentrifugal pump to cause it to evacuatethe air from its suction pipe and draw'liquid, which comprises throwinga mixture of air and liquid out of the discharge orifice, checking thevelocity of the mixture, separating the gas from the liquid, andreturning the liquid to the impeller to be mixed with gas within thepump and discharged out of the discharge orifice until the suction pipeis evacuated.

41. The method of operating a centrifugal no I pump to cause it toevaporete the air from its suction pipe and draw liquid, which comprisesthrowing a mixture of air and liquid out of the discharge orifice,checking the velocity .of the mixture, separating the gas form theliquid, and returning the'liquid to the impeller to be mixed with'gas 1nthe puinpand discharged out of the discharge lit 578,236

orifice until the suction pipe is evacuated and then throwing the excessof liqui I,0

which is' carried by the impeller out of the passage which previouslyserved as the return passage for liquid.

